1. Elevated phosphate levels in lakes and rivers can cause algal blooms and other problems. To protect e ecosystems, several strict pollution laws were enacted. Prior to these laws, the phosphate levels in a river had a true mean and variance of 650 ug/l and 640, respectively. After the laws were enacted, 12 water samples were found to have a sample mean of 500 ug/l. Assuming phosphate levels are normally distributed, perform a hypothesis test at a = 0.05 to see if phosphate levels were reduced after the laws these were enacted. 1.Hoi l= 650 Hai ll <6S0 2,& =0.05 3. under Ho: X-650 25.3/2 4.X= 500 s00 -650 25.3/Ta NCO,D = -20.54 5. P nalue 2. Documents from the whaling industry of Windward Islands in the Lesser Antilles indicate that in the 1920s short-finned pilot whales weighed an average of 360 kg. Cetologists believe that overhunting and depletion of prey species has caused the average weight of these whales to drop in recent years. A modern survey of this species in the same waters found that a random sample of 25 individuals had a mean weight of 336 kg and sample standard deviation of 30 kg. Using significance threshold a = 0.01, can you conclude that pilot whales are significantly lighter today than during the 1920s? 1. Ho: U = Ηα . μ. 2,2:0.01 3. under Ho: X- 4. 8 = 5. P walue

Glencoe Algebra 1, Student Edition, 9780079039897, 0079039898, 2018

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ISBN:9780079039897

Author:Carter

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Chapter10: Statistics

Section10.5: Comparing Sets Of Data

Problem 13PPS

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I'm started doing these, but I'm not sure if they are set up right. I am confused about the difference between a true variance and a sample standard deviation.

1. Elevated phosphate levels in lakes and rivers can cause algal blooms and other problems. To protect
e ecosystems, several strict pollution laws were enacted. Prior to these laws, the phosphate levels in
a river had a true mean and variance of 650 ug/l and 640, respectively. After the laws were enacted, 12
water samples were found to have a sample mean of 500 ug/l. Assuming phosphate levels are normally
distributed, perform a hypothesis test at a = 0.05 to see if phosphate levels were reduced after the laws
these
were enacted.
1.Hoi l= 650
Hai ll <6S0
2,& =0.05
3. under Ho:
X-650
25.3/2
4.X= 500 s00 -650
25.3/Ta
NCO,D
= -20.54
5. P nalue
2. Documents from the whaling industry of Windward Islands in the Lesser Antilles indicate that in the
1920s short-finned pilot whales weighed an average of 360 kg. Cetologists believe that overhunting and
depletion of prey species has caused the average weight of these whales to drop in recent years. A
modern survey of this species in the same waters found that a random sample of 25 individuals had a
mean weight of 336 kg and sample standard deviation of 30 kg. Using significance threshold a = 0.01,
can you conclude that pilot whales are significantly lighter today than during the 1920s?
1. Ho: U =
Ηα . μ.
2,2:0.01
3. under Ho: X-
4. 8 =
5. P walue

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